Bending apparatus for printing plates



June 8, 1965 F. HELLER 3,187,542

BENDING APPARATUS FOR PRINTING PLATES Original Filed Nov. 12, 1959 4 Sheets-Sheet 1 Pi/JIA??? INVENTOR. 5- 2444, BY %zare M-%z:-

ATTORNEYS June 8, 1965 F. HELLER 3,187,542

assume APIARATUS FOR munmw PLATES Original Filed Nov. 12, 1959 4 Shoots-Sheet 2 7 If y, n

I W\ Mg m IN V EN TOR.

June 8, 1965 F. HELLER BENDING APPARATUS FOR PRINTING PLATES 4 Sheets-Sheet 3 Original Filed Nov. 12, 1959 BY %m M ATTORNEYS June 1965 F. HELLER 3, 87,542

BENDING APPARATUS FOR PRINTING PLATES Original Filed Nov. 12, 1959 4 Sheets-Shea? 4 ATTORNEY$ United States Patent 3,187,542 BENDING APPARATUS FOR PRINTING PLATES Franz Heller, Mount Vernon, N.Y., assignor to American Type Founders Co. Inc., Elizabeth, NJ., a corporation of Delaware Original application Nov. 12, 1959, Ser. No. 852,260, now Patent No. 3,022,728, dated Feb. 27, 1962. Divided and this application Aug. 2, 1961, Ser. No. 128,760 Claims. (Cl. 72-321) This invention relates to certain preparatory steps concerned with the make-ready of a lithographic printing press, for example one of the web fed offset type, and has its principal object the provision of a novel apparatus for properly forming and applying the printing plates to the plate cylinders of the press.

This application is a division of my co-pending application Serial No. 852,260, filed November 12, 1959,,now Patent No. 3,022,728, dated February 27, 1962.

Workers in the printing industry are aware that the metal printing plates used in high-speed web offset presses must be very accurately applied to the cylinders for quality production, the height or projection of the surface of the plates above the cylinder bearers being measured in thousandths -of an inch. To this necessity of accurate packing and securing of the plates must be added the care in insuring that the plates are formed in the bending jig to the exact length appropriate to the circumference of the cylinders. Otherwise the plate is not securely held and continual flexing of the plate during operation of the press will cause the plate to crack, especially during long runs. This is particularly true in the case of aluminum plates.

Research by the applicant has also revealed another contributing factor in this proneness of the plate to crack. This further source of difliculty arises especially where a single reel-rod is employed in the cylinder gap, such a reel-rod functioning not only to pull the tail edge of the plate taut but to clamp or wedge the bent portion of the leading edge against an inwardly angled wall of the cylinder gap.

Now the conventional bending of the leading edge of the plate to an acute angled confiuration prepares it to fit over the similarly angled portion of the cylinder adjacent the gap, but no such strong pull is effected at the leading edge as is applied to the tail edge of the plate by the rotation of the reel-rod. As a consequence, it is difficult to insure that the curvature of the plate near its bent or hooked leading edge will conform to the exact radius of the cylinder. Thus there occurs a slight hump in the plate at this point witha minute air space formed between the humped portion of the plate and the cylinder body. Furthermore, the material of which the plate is made is under some stress adjacent the hump or bend, the outer surface of the plate probably being under tension and the inner surface under compression stresses of varying degrees. During the printing operation, as the form rollers and the blanket cylinder pass over this hump, the plate will be alternately depressed and released, and this repeated flexing of the plate will add further stress to the already stressed plate and cause it to crack, with the resulting added costs and inconvenience.

It has been suggested that this difficulty might be overcome by providing reel-rods for both ends of the plate in order to draw the plate more snugly against the cylinder at the forward end in the same manner that the reel rod accomplishes this purpose at the tail end, but these accessories occupy considerable space and increase printing costs, and would necessitate a much wider and uneconomical non-printing cylinder gap.

It is therefore an object of the present invention to provide novel methods and means for eliminating the forice mation of such a stressed hump in the plate near its leading edge, while at the same time preserving the accuracy of gauging the length of the plate in accordance with the circumference of the curved portion of the plate cylinder.

The invention contemplates the provision of a deliberately pre-formed bend or curvature just inwardly of the bent or hooked leading edge of the plate, this curvature being on a radius preferably not more than the radius of curvature of the cylinder itself. This expedient has been found to completely eliminate the bulging and consequent cracking of the printing plates at the points mentioned.

The invention also embraces the provision of a novel plate bending jig by means of which this pre-forming adjacent the leading edge may be accomplished.-

Other objects and features of novelty will be apparent from the following specification in which one embodiment of the invention is illustrated by way of example.

In the drawings:

FIGURE 1 is a somewhat diagrammatic view in side elevation of a printing plate in flat form after it has come out of a bending jig of conventional construction;

FIGURE 1A is a fragmentary diagrammatic view in end elevation of a plate cylinder showing in somewhat exaggerated style the initial application of the forward acutely bent portion of the plate as it is applied to the cylinder FIGURE 2 is a similar view showing in somewhat exaggerated style the destructive hump formed in the plate bent in the usual way adjacent the cylinder gap;

FIGURE 3 is a view similar to FIGURE 1 showing the pre-formed bend or curvature provided in the plate adjacent its leading edge according to the provisions of the present invention;

FIGURE 4 is a view similar to FIGURE 2 showing the snug application of the plate of such novel configuration to the plate cylinder;

FIGURE 5 is a somewhat diagrammatic view in side elevation of a jig embodying the principles of the invention;

FIGURE 6 is a view in end elevation of the jig as viewed from the left in FIGURE 5 FIGURE 7 is a fragmentary enlarged view in side elevation of the left-hand end of the jig with certain parts shown in section, as along line 7-7 of FIGURE 6;

FIGURE 8 is a further section-alized view of the same portion of the jig, for example, as taken on line 8-8 of FIGURE 6;

FIGURE 9 is a fragmentary sectional view taken on line 99 of FIGURE 6;

FIGURE 10 is a detail sectional view taken on line 10-10 of FIGURE 6;

FIGURE 11 is a fragmentary view in side elevation of the right-hand end of the jig as viewed in FIGURE 5;

FIGURE 12 is a plan view of the jig showing certain gauging means for insuring the proper positioning of a plate for bending; said means for the most part having been omitted from the preceding figures for the sake of simplicity and clearness of illustration;

FIGURE 13 is a fragmentary plan view of a portion of the jig including certain optical gauging means;

FIGURE 13A is -a fragmentary plan View in perspective of a portion of the upper surface of a plate showing the gauge marks used in positioning it; and

FIGURE 14 is a fragmentary view in vertical section taken on line 1414 of FIGURE 12.

In the views illustrative of the prior art set forth in FIGURES 1, 1A, and 2 of the drawings, the conventional printing plate which may be of zinc, copper, aluminum, or other substances familiar in the art, is designated generally by the reference numeral 10 and comprises a flat area 1 1 constituting the major portion of the plate and w carrying the printing areas thereof. At the left-hand end of the plate the leading edge is folded downwardly and reanwardly as at 12 to make an acute angle with the major portion 11. At the tail end of the plate the tail edge is given a double bend which includes portions 13 and 14, the function of which will appear upon a cursory examination of FIGURE 2 of the drawings.

In FIGURES 1A and 2 the plate cylinder is given the general designation 20 and is provided with a gap 21 having a narrowed portion 22 between projecting noselike edges of the body of the cylinder indicated at 23 and 24. Within the wider inward portion 25 of the gap 21 reel-rod 26 (FIGURE 2) is positioned for manual adjustment. The conventional plate It is applied to the periphery of the plate cylinder 20 with the bent portion 12 of the leading edge hooked as well as the acute angling of this portion of the plate permits around the nose 23 of the cylinder body (see FIGURE 1A). The extreme bent section 14 of the tail edge is gripped within the cleft 28 of the reel-rod and the circumference of the reel-rod 2 6 exertsa pullon the tail of the plate Iii, which due to the obtuse angular disposition of the tail flange 13 not only exerts the tension on the plate in a generally lengthwise direction but also draws it inwardly and quite snugly against the adjacent nose portion 24 of the gap 21.

Now in the case of the prior art plate illustrated dic. grammatically in FIGURE 1, the head end portion of the plate adjacent the front or head flange 12 tends to retain its acute angularity and the exposed portion of the plate to remain in a somewhat straight line, suggested at a, tangent to the circumference of the cylinder. This results from the lack of a direct inward pull as applied to the tail flange by a reel-rod. Then when the leading flange '12 is wedged against the inner wall surface 29 of the cylinder gap, along with the tail flange 13, the wedging and frictional efiect applied by the reel-rod exerts a pull along this wall 29, and not by way of the obtuse angle by which the tail flanges are drawn by the reel rod. This results in the formation of a curved or humped portion in the plate adjacent the apex of the bend of the flange 12 as shown in FIGURE 2 of the drawings in somewhat exaggerated form, an air space 31 being left beneath this portion of the "plate. Also, the plate adjacent this raised, humped, or

curved area is under stress, and it is understandable that the humped area. will have additional stresses applied to it in rapid alternation during the continual high speed rotation of the plate cylinder in contact with the blanket cylinder and the associated inking system, and this, es-

pecially in long runs, will cause the cent the hump and the leading flange.

So much for the existing situation with respect to conventional devices of this nature. Now,'referring particularly to FIGURES 3 and. 4 of the drawings, it will be seen that the novel plate conformation provided by the present invention and indicated generally by the reference numeral comprises a similar level portion 51 before it is applied to the cylinder, but toward the leading edge plate to crack adjaof the plate this major portion of the plate is given a definite downward curvature as shown at 55. The downwardly curved portion terminates in the usual hook portion 52 at the leading edge of the plate. The plate at .its tail end terminates in the double bend 53 and 54 as in the eanlier described structure.

FIGURE 4 merely shows the novel plate structure 58 applied to the plate cylinder 2b the major intelligence bearing portion 51 being wrapped around the cylinder in the usual way with the leading edge flange or hook portion 52 clamped in the gap 21 by means of the reel-rod 26 which grips the tail areas 13 and 14 and holds both ends of the plate firmlygripped within the gap. It will be noted that at the additional inwardly bent area 55 the plate hugs the cylinder surface snugly and'the hump such as shown at 30 in FIGURE 2 is completely eliminated.

Bearing in mind that the aim of the provision of the curvature or bend 55 is to cause the plate at this point to hug the underlying surface of the cylinder more closely in spite of the sharpness of the angularity of the flange 52, it will be readily understood that the degree of prebending at 55 will vary somewhat depending upon the size of the cylinder, the thickness of the plate, and the material of which it is formed, as well as the temper or hardness of the plate material. Furthermore, the curvature of the bend, that is the radius indicated at r in FIG- URE 3, is not critical and becomes even less so as the diameters of the cylinders increase. However, it might be mentioned that the radius r will in most cases be less than the radiuso'f the cylinder itself since in the case of a plate of more than usual resilience, a slight over-bending may be necessary to compensate for any spring-back which might occur. Thus, it may be stated broadly that the radius r may be anywhere from that of the cylinder down to a value considerably less than the radius of the cylinder.

The process thus described may be carried out by means of the novel plate bending jig which is given the general designation 60 as illustrated in the remaining figures of drawing. In the somewhat diagrammatic view comprising FIGURE 5, it will be seen that the body of the jig 60 comprises two base blocks 61 and 62, these blocks being mounted upon the guiding and supporting,

strips or runners 63. The base is made in two parts so that they may be adjusted with relation to each other to accurately determine the proper over-all length of the plate to conform to the circumference of the particular plate cylinder, a space 64 being left between the blocks 61 and 62 for this purpose.

The left-hand base block 61 is formed at its extremity with a projecting ledge or nose portion 65 which is most clearly shown in FIGURES 7 and 8 of the drawings. The angularity of this projecting ledge may of course vary somewhat and a suggested angle useful for most purposes is approximately 35. The extreme apex or point 66 of the ledge es isslightly rounded, preferably on a radius of approximately 0.05 of an inch, taken on the center of the pintle 76.

However, the most radical feature of the bending ledge 65 is the provision of the curvature near the ex treme edge thereof in the area designated '70. This curvature is provided in order to form'the preliminary bend 55 in the plate 50 adjacent the leading edge.

Extending from each side of the left-hand edge of the base block 61 are a pair of brackets 72, these rather flat brackets being secured to the respective sides of the base 60 as by means of the screws73. These brackets 72 haveprojecting ears provided with registered threaded openings 75. Pintles 76 are threaded into the openings 75, each of these pintles having an inwardly projecting attenuated unthreaded portion 77 terminating in a rounded tip 78. Fixed to the outer ends of the spindles 76 are the hand wheels or knobs 79.

A bending bar 80 extends transversely across the jig just off of the nose or ledge portion'65 and is provided at each of its ends with a hinge bracket plate 81, these plates being provided with-openings 82 to receive the cylindrical portion 77 of the pintle or spindle members 76. Thus, the bending bar 80 is mounted with one of the lower corners thereof'substantially coinciding with the apex or ultimate edge 66 of the bending ledge 65. Extending outwardly from the bar 84 is the bracing and supporting framework 85 surmounted by the handle portion 86.

Each of the brackets 72 is provided with openings extending vertically downwardly therethrough and adapted to fixedly secure the lower ends of the pins or posts indicated at 88. These openings occur just beneath the curved portion 70 of the bending ledge 65, and immediately above this curved portion is positioned the preliminary bending and clamping bar 98 which 'has a bottom surface 91 conforming to the curvature of the portion 70 of the block 61 and of the desired preliminary bend to be impressed upon the plate 50 adjacent its leading edge. The clamp bar 90 is provided at its left-hand end as viewed in FIGURE 6 with a notch or kerf 92 extending in the longitudinal direction, and at its right-hand end with a transversely extending notch or kerf 94. The end notch 92 virtually comprises a fork which is made to straddle the intermediate portion of the threaded post 88 at that end of the device, the lower end of the cylindrical wheeled head 95 threaded upon the spindle bearing downwardly upon the upper surface of that end of the clamping bar 90 adjacent the kerf 92. The right-hand end of the clamp bar 90 may be swung into position beneath the wheeled head 96 applied to the post 88 at that end of the clamp bar so that the notch or kerf 94 embraces the stern of the spindle as most clearly known in FIGURE 9 of the drawings. The head 96 threaded onto the post 88 at this end of the device bears downwardly upon the upper surface of the clamping bar 90 as in the case of the left-hand end.

The clamping bar 90 is provided with a bowed truss element 98 to insure its rigidity.

In order to facilitate the installation of the bending bar 80 upon the spindles 76, a pair of rests or supporting brackets 100 are secured to the bending bar 80 and have portions 101 which overlie the clamp bar 90 and are allowed to rest upon the clamp bar in order to support the weight of the bending bar during the time that the spindles 76 are threaded through the openings 75 in the hanger brackets 72.

At the tail end of the jig, as indicated in FIGURES 5 and 11, there is provided a clamp bar 110 which in most respects is the counterpart of the clamp 90 at the leading end, except that the bottom surface 111 is perfectly fiat and not provided with a curve such as characterizes the leading edge of the arrangement. Stitfening and bracing superstructure 112 is provided for the clamping bar and the bar 110 is brought to bear downwardly upon the plate as by means of the hand wheels or knobs 95' and 96'.

In order to throw the double bend into the tail end of the plate as represented by the parts 53 and 54 a bending bar 125 is provided, this bending bar being provided at each end with the hinge plate 126 which is adapted to be connected by a pintle 127 with the corresponding hinge plate 128 secured to the tail end of the base block 62 of the jig. Obviously, the pintle 127 is centered upon the edge or corner 129 of the block 62. The end of the block 62 is provided with a sloping surface 130 which merges at 131 with the downwardly and inwardly inclined surface 132. The bending bar 125 has a flat lower surface 136 and a supplemental bar 140 is secured to the side of the bending bar 125, this supplemental bar being provided with an inclined surface 142.

The bending bar 125 is provided with a stiffening superstructure 145 surmounted by an operating handle 146 as in the case of the bending bar 80 at the other end of the jig.

Referring now more particularly to FIGURES 12 to 14 of the drawings, certain gauge devices for properly positioning the plate'on the jig will be described. Midway along each side of the body of the jig 60, bringing the gap 64 between the blocks 61 and 62, are the fixed plates or inserts 150. These small plates have inscribed thereon, with a great degree of accuracy, the rectilinear gauge markings 151. These gauge marks project slightly beyond the end margins of the printing plate P indicated by the lines 152. Similar register marks 151' are inscribed on the printing plate and these are brought into exact alignment with the gauge marks 151 on the insert 150.

Other and somewhat more accurate gauging and aligning means are provided by the optical devices commonly called scopes and indicated at 155, 156, 157 and 158 in FIGURE 12 of the drawings. Two of these scopes, designated 155 and 156, are carried by brackets 160 and 161, which are disposed at an angle with respect to the margin of the plate P to be bent, and the scopes 157' and 158 are carried in the rectilinearly disposed brackets 162 and 163. The scope 158 and its bracket 163 are shown to advantage upon an enlarged scale in FIGURES 13 and 14 of the drawings.

Directly beneath the position which the scope 158 will occupy, the base block 61 is drilled to provide a recess or pocket 165 and fixed within the recess is a cylindrical block 166 preferably made of brass and inscribed upon its upper sunface with cross lines as at 167. The-re are four of these blocks 166, one beneath each of the scopes adjacent to the four corners of the plate, and they serve as bench marks for accurately predetermining and checking the linear and transverse measurements between the cross-hairs of adjacent scopes.

The bracket 163 as shown in FIGURES 13 and 14, has its shank end drilled at three places to receive the bolt 168 and the dowel pins 169. Bolt 168 is threaded into the base block 61 as as 170 and the dowel pins 169 are fitted closely in hardened steel bushings 172 which are pressed into the recess 173 in the block.

The forward end of the bracket 163 is bifurcated as at 175 and adapted to receive the optical scope 158 which is of cylindrical configuration and may be provided with any suitable system of lenses, suggested at 176, and with cross-hairs 177 which are brought into exact register with the cross marks 167 on the brass block 166 for a preliminary setting. The bifurcated end 175 of the bracket 163 may be brought into close gripping contact with the scope 158 by means of the bolt 179. It will be noted that the forward end of the bracket 163 is indicated to provide a slot 180 for the reception of the edge of the plate P. The plate P, as shown in FIGURE 13, is provided with cross gauge marks 187 which will be brought into alignment with the crosshairs 177 of the scope 158 when the plate is in properly located position.

The scope and bracket installation 1'57, 162 will be identical with the one just described in connection with FIGURES 13 and 1-4 of the drawings, except in reversed position. The scopes 155 and 156 (160 and 161) are similarly formed, equipped, and fastened, except that they are disposed at a 45 angle with the edges 152 of plate P, and the undercut or notched portion 180 is V shaped at its inner extremity as clearly shown in the upper portions of FIGURE 12.

The operation of the device in forming the novel plate configurations will be readily understood from the following description: The clamping bars and as well as the bending bars 80 and are removed from the jig and the plate P is placed on the jig and lined up, according to one method, by bringing the inscribed lines or register marks 151 on the plate P into alignment with the inscribed gauge marks 151 on the insert at either side of the jig. The register marks 151' are placed on the plate by. the plate maker in accurate relation to the image on the plate. This will locate the plate quite accurately in the jig. Then the clamp bars are replaced into position, the plate securely clamped adjacent its ends, the bending bars installed, and then swung downwardly to throw the bends into therespective ends of the plate.

In using the scopes, the operator will locate the plate approximately on the bending jig, then place the clamp bars in position and snug down the plate on the jig. He will then take the four optical scopes as they are mounted on their supporting brackets and place the assembly into position over the plate. He will next move the plate until the four register marks inscribed on the plate coincide with the cross hairs in the four scopes. Finally, he will clamp the plate tightly and make the bends.

At any time during the life of the bending jig the operator can check the accuracy of the scopes against F the cross-hairs which are permanently located on the jigs on the plugs 166.

In the bending operation, the movement of the leading edge bending bar 80 is clearly shown in FIGURE 8 of the drawings, the initial position being indicated in solid lines and the dotted line position showing the ultimate end of the swinging movement Where the hook portion of the plate has been swung downwardly and inwardly against the underside of the ledge 65. At the tail end of the device the downwardly swinging movement of the bending bar 125, 140 from the solid line position to the dotted line position effects the double bend in that end of the plate. v

Upward swinging return movement of the bending bars and the releasing of the clamping bars frees the plate for removal and application to the plate cylinder of the press.

It is understood that various changes and modifications may be made in the illustrative embodiment of the invention set forth herein without departing from the scope of the invention as defined by the following claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

'1. A plate bending jig for conforming a lithographic printing plate to a configuration suitable for the proper and accurate fitting thereof to the plate cylinder of an oifset printing press, said jig comprising a base having a planar top surface for the major portion of its extent, transversely extending clamping bars at each end of said base, the Width of each of said clamping bars as related to. the entire width of the base being quite small whereby by far the major portion of the base is free of pressing or confining structure, means for applying pressure to said clamping bars to cause them to firmly clamp the plate against the base only adjacent the ends thereof, a fixed downwardly curved portion at one end only of the top surface of said base and a corresponding curved lower face on the narrow clamping bar at that end of the jig only, whereby a narrow arcuate bend is formed in the plate adjacent its leading edge, bending bars pivotally connected to the ends of said base independently of said clamping bars, the length of the base being less than that of the plate whereby the end edges of the plate overhang, means for pivotally supporting said bending "bars from the base itself and for swinging movement about the end edges of the base surface to cause the edges of the plate to conform thereto and thus provide attaching flanges on the latter, in addition to the narrow arcuate bend in the otherwise fiat medial portion of the plate.

2. A plate bending jig for conforming a lithographic printing plate to a configuration suitable for the proper and accurate fitting thereof to the plate cylinder of an offset printing press, said jig comprising a base having a planar top surface for the major portion of its extent, transversely extending clamping bars at each end of said base, means for applying pressure to said clamping bars to cause them to firmly clamp the plate against the base adjacent the ends thereof, bending bars pivotally connected to the ends of said base,'the length of the base being less than that of the plate itself whereby the end edges of the; plate overhang, means for pivotally support ing said bending bars from the base and for swinging movement about the end edges of the base to cause the edges of the plate to conform thereto and thus provide attaching flanges on the latter; and provisions for the ready removal of said clamping bars from the jig, said provisions including vertical bores in the ends portions of the clamp ing bars and threaded posts extending upwardly from the base through said vertical bores and carrying threaded knobs adapted to bear upon the upper surfaces of the clamping bars, and kerfs cut horizontally into the clamping bars and intersecting said vertical bores so that when the threaded knobs are loosenedthe clamping bars may be removed horizontally, the posts passing through said kerfs.

3. A plate bending jig for conforming a lithographic printing plate to a configuration suitable for the proper and accurate fitting thereof to the plate cylinder of an offset printing press, said jig comprising a base having a planar top surface for the major portion of its extent, transversely extending clamping bars at each end of said base, means for applying pressure to said clamping bars to cause them to firmly clamp the plate against the base adjacent the ends thereof, bending bars pivotally connected to the ends of said base, the length of the base being less than that of the plate itself whereby the end edges of the plate overhang, means for pivotally supporting said bending bars from the base andfor swinging movement about the end edges of the base to cause the edges of the plate to conform thereto and thus provide attaching flanges on the latter; and provisions for the ready removal of said bending bars, said provisions including trunnion brackets extending from the ends of the base and having threaded horizontal bores extending therethrough, trunnion pins threaded through said bores and having enlarged manually operable heads and inwardly projecting ends entering openings in the end portions of said bending bars to provide pivots therefor, said bending bars being readily removable upon retraction of said trunnion pins by manual actuation of said heads.

4. A plate bending jig for'conforming a lithographic printing plate to a configuration suitable for the proper and accurate fitting thereof to the plate cylinder of an offset printing press, said jig comprising a base having a planar top surface for the major portion of its extent, transversely extending clamping bars at each end of said base, means for applying pressure to said clamping bars to cause them to firmly clamp'the plate against the base adjacent the ends thereof, bending bars pivotally connected to the ends of said base, the length of the base being less than that of the plate itself whereby the end edges of the plate overhang, means for pivotally supporting said bending bars from the base and for swinging movement about the end edges of the base to cause the edges of the plate to conform thereto and thus provide attaching flanges on the latter; and provisions for the ready removal of both said clamping bars and said bending bars, said provisions comprising a bracket fixedly secured to and forming a part of said base ateach side of each end thereof, threaded ports extending upwardly from said brackets through vertical bores in the clamp ing bars and carrying threaded knobs adapted to bear upon the upper surfaces of the clamping bar, horizontally extending kerfs cut in said clamping bars and intersecting said vertical bores whereby when said threaded knobs are loosened the clamping bars may be readily removed horizontally, the posts passing through said kerfs; horizontal threaded bores in said brackets, headed trunnion pins threaded through said bores and having enlarged manually operable heads and inwardly projecting ends entering openings in the end portions of said bending bars to provide pivots therefor, the bending bars being readily r movable upon retraction of said trunnion pins by manual actuation of said heads.

5. A plate bending jig for conforming a lithographic printing plate to a configuration suitable for the proper and accurate fitting thereof to the plate cylinder of an offset printing press, said jig comprising a base having a planar top surface for the major portion of its extent and end edge portions angleddownwardly, transversely extending clamping bars at each end of said base, means for applying pressure to said clamping bars to cause them to firmly clamp the plate against the base adjacent the ends thereof, said last named means comprising threaded posts extending upwardly from the base through openings in the end of the clamping bar and carrying threaded knobs adapted to bear upon the upper surfaces of the clamping bar, a downwardly curved portion at one end of said base just inwardly of the angled edge at said end and a corresponding curved lower face on the clamping bar at that end of the jig, whereby an arcuate bend is formed in the plate adjacent its leading edge, and bending bars pivotally connected to the ends of said base independently of said clamping bars, the length of the base being less than that of the plate itself whereby the end edges of the plate overhang, said bending bars being mounted to swing about a center coincident with the center of the curved or angled end edges of the base to References Cited by the Examiner UNITED STATES PATENTS Weaver 153-17 Pirwitz 83-521 Vandercook 83-521 Jensen.

Green 153-33 Larkin 153-17 cause the edges of the plate to conform thereto and thus 10 CHARLES W LANHAM Primary Examiner provide attaching flanges on the latter. 

1. A PLATE BENDING JIG FOR CONFORMING A LITHOGRAPHIC PRINTING PLATE TO A CONFIGURATION SUITABLE FOR THE PROPER AND ACCURATE FITTING THEREOF TO THE PLATE CYLINDER OF AN OFFSET PRINTING PRESS, SAID JIG COMPRISING A BASE HAVING A PLANAR TOP SURFACE FOR THE MAJOR PORTION OF ITS EXTENT, TRANSVERSELY EXTENDING CLAMPING BARS AT EACH END OF SAID BASE, THE WIDTH OF EACH OF SAID CLAMPING BARS AS RELATED. TO THE ENTIRE WIDTH OF THE BASE BEING QUITE SMALL WHEREBY BY FAR THE MAJOR PORTION OF THE BASE IS FREE OF PRESSING OR CONFINING STRUCTURE, MEANS FOR APPLYING PRESSURE TO SAID CLAMPING BARS TO CAUSE THEM TO FIRMLY CLAMP THE PLATE AGAINST THE BASE ONLY ADJACENT THE ENDS THEREOF, A FIXED DOWNWARDLY CURVED PORTION AT ONE END ONLY OF THE TOP SURFACE OF SAID BASE AND A CORRESPONDING CURVED LOWER FACE ON THE NARROW CLAMPING BAR AT THAT END OF THE JIG ONLY, WHEREBY A NARROW ARCUATE BEND IS FORMED IN THE PLATE ADJACENT ITS LEADING EDGE, BENDING BARS PIVOTALLY CONNECTED TO THE ENDS OF SAID BASE INDEPENDENTLY OF SAID CLAMPING BARS, THE LENGTH OF THE BASE BEING LESS THAN THAT OF THE PLATE WHEREBY THE END EDGES OF THE PLATE OVERHANG, MEANS FOR PIVOTALLY SUPPORTING SAID BENDING BARS FROM THE BASE ITSELF AND FOR SWINGING MOVEMENT ABOUT THE END EDGES OF THE BASE SURFACE TO CAUSE THE EDGES OF THE PLATE TO CONFORM THERETO AND THUS PROVIDE ATTACHING FLANGES ON THE LATTER, IN ADDITION TO THE NARROW ARCUATE BEND IN THE OTHERWISE FLAT MEDIAL PORTION OF THE PLATE. 